Composite article

ABSTRACT

A composite article includes an acrylic layer, a UV-cured layer formed from a UV-curable composition, and a polyurethane backing layer. A method of forming the composite article includes applying the UV-curable composition to the acrylic layer such that the composition is between the acrylic layer and the polyurethane backing layer to enhance bonding between these layers. The UV-curable composition includes at least one monomer which is an ethylenically unsaturated methacrylate monomer, an ethylenically unsaturated acrylate monomer, or both. The at least one monomer has a hydroxy functional group. The monomer is compatible with the acrylic layer and the hydroxy functional group of the monomer is reactive with a polyisocyanate from the polyurethane backing layer. The UV-curable composition also includes a curing initiator that is reactive with the monomer. Upon exposure of the UV-curable composition to UV electromagnetic radiation, the curing initiator enables the composition to cure to the acrylic layer.

FIELD OF THE INVENTION

[0001] The subject invention generally relates to a composite articleincluding an acrylic layer, a polyurethane layer and a UV-cured layerformed from a UV-curable composition, and a method of forming thecomposite article using the UV-curable composition. The compositearticle and the method used in forming the composite article may beutilized in the boating, automobile, swimming pool, and bathtubindustries. The subject invention more specifically relates to aUV-curable composition that is applied between an acrylic layer and apolyurethane layer in a composite article to enhance bonding betweenthese layers.

BACKGROUND OF THE INVENTION

[0002] Use of composite articles throughout the boating, automobile,swimming pool, and bathtub industries is known in the art. Prior artcomposite articles include those comprising a first layer of styrenatedpolyester and a second layer of polyurethane. As understood by thoseskilled in the art, the first layer is a top layer, or show surface, ofthe composite article, and the second layer is a backing layer of thecomposite article that functions to provide support and durability tothe completed composite article.

[0003] It is known in the art that during application of the first layerof styrenated polyester to a mold substrate large quantities of styrenemonomers, which are considered volatile organic compounds (VOCs), areemitted and this is undesirable for environmental, health, and safetyreasons. Large quantities of other VOCs, such as methyl ethyl ketone,are also typically emitted during application and cross-linking of thestyrenated polyester first layers of the prior art. Emission of theseother VOCs is also undesirable for environmental, health, and safetyreasons. Additionally, the cross-linking of the styrenated polyesterfirst layers typically requires extended cures including exposure toincreased temperatures. It is understood in the art that such cures arecostly and time consuming.

[0004] Furthermore, because the first layer of the composite article isthe show surface of the composite article, the composite articles of theprior art that include styrenated polyester as the first layer areexcessively brittle and suffer from cracking and chipping defects due tothis excessive brittleness characteristic of styrenated polyesters. Suchdefects become particularly apparent during shipping, handling,transportation, and use of the composite articles.

[0005] Finally, the composite articles having styrenated polyester-basedshow surfaces, as well as other composite articles of the prior art, aredeficient because their show surface is unstable under prolongedexposure to ultraviolet light.

[0006] Due to the many difficulties associated with the styrenatedpolyesters as set forth above, it is desirable to form compositearticles having top layers or show surfaces formed of acrylic instead ofstyrenated polyester. The composite articles of the prior art havingacrylic show surfaces, however, have not been able to form a suitablecohesive bond between the polyurethane backing layer and the acrylicshow surface. Consequently, these composite articles have extremely poorinter-layer adhesion between the polyurethane backing layer and theacrylic show surface resulting in delamination and susceptibility tochip and other defects of the composite article.

[0007] In view of the deficiencies identified in the composite articlesof the prior art, it has been desirable to provide a novel and uniqueUV-curable composition, composite article including the UV-curablecomposition, and method of forming the composite article using theUV-curable composition. Specifically, it is desirable to provide aUV-curable composition that can be applied between acrylic andpolyurethane layers of a composite article to enhance bonding betweenthese layers and to optimize certain physical properties of thecomposite article.

SUMMARY OF THE INVENTION

[0008] A composite article including a UV-cured layer formed from aUV-curable composition, and a method of forming the composite articleusing the UV-curable composition are disclosed. The composite articleincludes an acrylic layer, a polyurethane layer, and the UV-cured layerformed from the UV-curable composition. The UV-curable composition isapplied between the acrylic layer and the polyurethane layer to enhancebonding between the acrylic layer and the polyurethane layer. TheUV-curable composition is applied to the acrylic layer. The polyurethanelayer is the reaction product of a polyol resin and a stoichiometricexcess of polyisocyanate.

[0009] More specifically, the UV-curable composition includes at leastone monomer including an ethylenically unsaturated methacrylate monomer,an ethylenically unsaturated acrylate monomer, or combinations thereof.The monomer is compatible with the acrylic layer. Furthermore, themonomer includes a hydroxy functional group which is reactive with thepolyisocyanate from the polyurethane layer. The UV-curable compositionfurther includes a curing initiator reactive with the monomer. Uponexposure of the UV-curable composition to UV electromagnetic radiation,the curing initiator reacts with the monomer thereby enabling theUV-curable composition to cure to the acrylic layer.

[0010] Accordingly, the subject invention offers a novel and uniqueUV-curable composition, composite article including the UV-cured layerformed from the UV-curable composition, and method of forming thecomposite article using the UV-curable composition. More specifically,the composite article of the subject invention, in addition to theUV-cured layer, includes an acrylic layer and a polyurethane layer. TheUV-curable composition is applied between the acrylic layer and thepolyurethane layer to enhance bonding such that the physical propertiesof the composite article, such as bond strength, are optimized.

DETAILED DESCRIPTION OF THE INVENTION

[0011] A UV-curable composition is disclosed. A composite article,including a UV-cured film layer formed from the UV-curable composition,and a method of forming the composite article using the UV-curablecomposition are also disclosed. The composite article includes anacrylic layer, a UV-cured layer, and a polyurethane layer.

[0012] The UV-curable composition and the polyurethane layer are appliedto the acrylic layer to form the composite article. As described ingreater detail below, the acrylic layer is provided by vacuum forming anacrylic-based coating composition. After the acrylic layer has beenvacuum formed and mounted on a separate form, primarily for support, theUV-curable composition is applied to the acrylic layer mounted on theform. The UV-curable composition is then cured. After the UV-curablecomposition has been cured thereby forming the UV-cured layer, thepolyurethane layer is applied, preferably spray applied, to the UV-curedlayer and allowed to cure. The acrylic layer, the UV-cured layer, andthe polyurethane layer, forming the composite article, are thende-molded. The acrylic layer is a top layer or show surface of thecompleted composite article, and the polyurethane layer is a backinglayer that functions to provide support and durability to the completedcomposite article. As a result, the polyurethane layer of the subjectinvention is hereinafter described as the polyurethane backing layer.Preferably, the acrylic layer is an acrylic-based substrate used in theboating, automobile, swimming pool, and bathtub industries. Mostpreferably, the acrylic-based substrate is a show surface of a bathtub.

[0013] The polyurethane backing layer, formed of a polyurethane-basedcoating, is the reaction product of a polyol resin and a stoichiometricexcess of polyisocyanate. The polyol resin includes, among othercomponents, at least one polyol. Preferably, the polyol resin includes aplurality of polyols. Although polyether polyols are preferred, the atleast one polyol may also include polyester polyols.

[0014] Suitable polyols in the polyol resin include, but are not limitedto, phthalic anhydride-initiated polyester polyols, aromaticamine-initiated polyols, aliphatic amine-initiated polyols,polyoxyalkylene polyether polyols, polycaprolactone polyols,polythioether polyols, polyester amides and polyacetals containinghydroxyl groups, aliphatic polycarbonates containing hydroxyl groups,amine terminated polyoxyalkylene polyethers, polyester polyols, otherpolyoxyalkylene polyether polyols, graft dispersion polyols, andcombinations thereof.

[0015] Included among the polyoxyalkylene polyether polyols arepolyoxyethylene polyols, polyoxypropylene polyols, polyoxybutylenepolyols, polytetramethylene polyols, and heteric and block copolymers.The block copolymers may include, for example combinations ofpolyoxypropylene and polyoxyethylene, poly-1,2-oxybutylene andpolyoxyethylene polyols, poly-1,4-tetramethylene and polyoxyethylenepolyols, and copolymer polyols prepared from blends or sequentialaddition of two or more alkylene oxides. The polyoxyalkylene polyetherpolyols may be prepared by any known process such as, for example, theprocess disclosed by Wurtz in 1859, Encyclopedia of Chemical Technology,Vol. 7, pp. 257-262, published by Interscience Publishers, Inc. (1951)or in U.S. Pat. No. 1,922,459. The alkylene oxides may be added to theinitiator compound individually, sequentially one after the other toform blocks, or in mixtures to form a heteric polyether. Thepolyoxyalkylene polyether polyols may have either primary or secondaryhydroxyl groups.

[0016] The polyoxyalkylene polyether polyols may be aromaticamine-initiated or aliphatic amine-initiated polyoxyalkylene polyetherpolyols. The amine-initiated polyols may be polyether polyols terminatedwith a secondary hydroxyl group through addition of, for example,propylene oxide as the terminal block. It is preferred that theamine-initiated polyols contain 50 weight percent or more, and up to 100weight percent, of secondary hydroxyl group forming alkylene oxides,such as polyoxypropylene groups, based on the weight of all oxyalkylenegroups. This amount can be achieved by adding 50 weight percent or moreof the secondary hydroxyl group forming alkylene oxides to the initiatormolecule in the course of manufacturing the polyol.

[0017] As described above, suitable initiator compounds for the polyolinclude primary or secondary amines. These would include, for thearomatic amine-initiated polyether polyol, the aromatic amines such asaniline, N-alkylphenylene-diamines, 2,4′-, 2,2′-, and4,4′-methylenedianiline, 2,6- or 2,4-toluenediamine, vicinaltoluenediamines, o-chloro-aniline, p-aminoaniline,1,5-diaminonaphthalene, methylene dianiline, the various condensationproducts of aniline and formaldehyde, and the isomeric diaminotoluenes,with preference given to vicinal toluenediamines.

[0018] For the aliphatic amine-initiated polyol, any aliphatic amine,whether branched or unbranched, substituted or unsubstituted, saturatedor unsaturated, may be used. These would include, as examples, mono-,di-, and trialkanolamines, such as monoethanolamine, methylamine,triisopropanolamine; and polyamines such as ethylene diamine, propylenediamine, diethylenetriamine; or 1,3-diaminopropane, 1,3-diaminobutane,and 1,4-diaminobutane. Preferable aliphatic amines include any of thediamines and triamines, most preferably, the diamines.

[0019] The polyoxyalkylene polyether polyols may generally be preparedby polymerizing alkylene oxides with polyhydric amines. Any suitablealkylene oxide may be used such as ethylene oxide, propylene oxide,butylene oxide, and combinations of these oxides. The polyoxyalkylenepolyether polyols may be prepared from other starting materials such astetrahydrofuran and alkylene oxide-tetrahydrofuran mixtures;epihalohydrins such as epichlorohydrin; as well as aralkylene oxidessuch as styrene oxide.

[0020] Also suitable are polymer modified polyols, in particular, theso-called graft polyols. Graft polyols are well known to the art and areprepared by the in situ polymerization of one or more vinyl monomers,preferably acrylonitrile and styrene, in the presence of a polyetherpolyol, particularly polyols containing a minor amount of natural orinduced unsaturation. Methods of preparing such graft polyols may befound in columns 1-5 and in the Examples of U.S. Pat. No. 3,652,639; incolumns 1-6 and in the Examples of U.S. Pat. No. 3,823,201; in columns2-8 and in the Examples of U.S. Pat. No. 4.690.956; and in U.S. Pat. No.4,524,157; all of which patents are herein incorporated by reference.

[0021] Non-graft polymer modified polyols are also suitable, forexample, as those prepared by the reaction of a polyisocyanate with analkanolamine in the presence of a polyether polyol as taught by U.S.Pat. Nos. 4,293,470; 4,296,213; and 4,374,209; dispersions ofpolyisocyanurates containing pendant urea groups as taught by U.S. Pat.No. 4,386,167; and polyisocyanurate dispersions also containing biuretlinkages as taught by U.S. Pat. No. 4,359,541. Other polymer modifiedpolyols may be prepared by the in situ size reduction of polymers untilthe particle size is less than 20 μm, preferably less than 10 μm.

[0022] In a preferred embodiment of the subject invention, the polyolresin of the polyurethane backing layer includes a first and a secondpolyol. Preferably, the first polyol, a polyether polyol, is present inan amount of from 35 to 55, more preferably from 40 to 50, parts byweight of the polyol resin. The first polyol is preferably atrimethylolpropane-initiated polyether polyol having a hydroxyl numberof from 25 to 45 meq polyol/g KOH and an average functionality of from 2to 3. More preferably, the hydroxyl number of the first polyol is from30 to 40 meq polyol/g KOH and the average functionality of the firstpolyol is from 2.4 to 2.8. A suitable first polyol is commerciallyavailable as Pluracol® 538 from BASF Corporation.

[0023] The second polyol, also a polyether polyol, is preferably presentin an amount of from 10 to 30, more preferably from 15 to 25, parts byweight of the polyol resin. The second polyol is preferably a vicinaltoluenediamine-initiated polyether polyol having a hydroxyl number offrom 300 to 500 meq polyol/g KOH and an average functionality of from 3to 5. More preferably, the hydroxyl number of the second polyol is from350 to 450 meq polyol/g KOH and the average functionality of the secondpolyol is from 3.5 to 4.5. A suitable second polyol is commerciallyavailable as Pluracol® 736 from BASF Corporation.

[0024] In addition to the at least one polyol, the polyol resin mayfurther include a supplemental chain extender. The chain extender ispreferably a diol or a mixture of diols. Such diols preferably includeany aliphatic, cycloaliphatic, and/or araliphatic diol having from 2 to14 carbon atoms, more preferably from 4 to 10 carbon atoms. Thesupplemental chain extender helps achieve desired physical properties ofthe polyurethane backing layer and therefore in the overall compositearticle.

[0025] Preferably, the diol selected is diethylene glycol (DEG).Alternative chain extenders include, but are not limited to, ethyleneglycol, propylene glycol, 1,4-butanediol, 1,5-pentane diol,1,6-hexanediol, 1,3-propanediol, 1,10-decanediol, o-, m-, andp-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, primaryand secondary aromatic diamines, 3,3′-di- and/or 3,3′-,5,5′-tetraalkyl-substituted diaminodiphenyl-methanes, andbis(2-hydroxyethyl)hydroquinone. The chain extender typically has anumber average molecular weight of less than 400, preferably from 60 to300 and is present in an amount of from 10 to 30, more preferably from14 to 20, parts by weight based on 100 parts by weight of the polyolresin. Triols such as 1,2,4- and 1,3,5-trihydroxycyclohexane, glycerol,and trimethylolpropane, and combinations thereof can also be used aschain extenders. The polyurethane backing layer can also be prepared byusing mixtures of diols and triols as the chain extenders.

[0026] The polyol resin may also include one or more additives directedat enhancing the performance of one or more physical properties of thecomposite and/or the polyurethane backing layer. For instance, theadditive or additives may be selected from the group consisting ofsurfactants, cell regulator, flame retardants, fillers, dyes, waterscavengers, anti-foam agents, catalysts, UV performance enhancers,pigments, hindered amine light stabilizers, and combinations thereof.Other suitable additives include, but are not limited to, cellregulators, hydrolysis-protection agents, fungistatic and bacteriostaticsubstances, dispersing agents, adhesion promoters, and appearanceenhancing agents. Although the subject invention is not intended to belimited to these examples, some specific examples of these additivesinclude aluminum tri-hydrate, calcium carbonate, gypsum, wollastonite,phosphorus, silica, glass including glass beads, calcium sulfate, andmagnesium hydroxide.

[0027] A catalyst may be employed as an additive to greatly acceleratethe reaction between the polyol resin and the polyisocyanate of thepolyurethane backing layer. Examples of suitable catalysts areorganometallic catalysts, preferably organotin catalysts, although it ispossible to employ metals such as aluminum, zirconium, lead, titanium,copper, mercury, cobalt, nickel, iron, vanadium, antimony, andmanganese. Suitable organometallic catalysts, exemplified here by tin asthe metal, are represented by the formula: R_(n)Sn[X—R¹—Y]₂, wherein Ris a C₁-C₈alkyl or aryl group, R¹ is a C₁-C₁₈methylene group optionallysubstituted or branched with a C₁-C₄alkyl group, Y is hydrogen or ahydroxyl group, preferably hydrogen, X is methylene, an —S—, an—SR²COO—, —SOOC—, an —O₃S—, or an —OOC— group wherein R² is a C₁-C₄alkyl, n is 0 or 2, provided that R¹ is C₀ only when X is a methylenegroup.

[0028] Specific examples of suitable catalysts are tin (II) acetate, tin(II) octanoate, tin (II) ethylhexanoate and tin (II) laurate; anddialkyl (from 1 to 8 carbon atoms) tin (IV) salts of organic carboxylicacids having 1-32 carbon atoms, preferably 1-20 carbon atoms, e.g.,diethyltin diacetate, dibutyltin diacetate, dibutyltin dioctoate,dibutyltin dilaurate, dibutyltin maleate, dihexyltin diacetate, anddioctyltin diacetate. Other suitable organotin catalysts are organotinalkoxides and mono or polyalkyl (from 1 to 8 carbon atoms) tin (IV)salts of inorganic compounds such as butyltin trichloride, dimethyl- anddiethyl- and dibutyl- and dioctyl- and diphenyl- tin oxide, dibutyltindibutoxide, di(2-ethylhexyl) tin oxide, dibutyltin dichloride, anddioctyltin dioxide. Preferred, however, are tin catalysts withtin-sulfur bonds which are resistant to hydrolysis, such as dialkyl(from 1 to 20 carbon atoms) tin dimercaptides, including dimethyl-,dibutyl-, and dioctyl-tin dimercaptides.

[0029] As for catalysis of the reaction between the polyol resin and thepolyisocyanate, in addition to the catalysts already identified above,tertiary amines may also be used to promote urethane linkage formationin the polyurethane backing layer. These amines include triethylamine,3-methoxypropyldimethylamine, triethylenediamine, tributylamine,dimethylbenzylamine, N-methyl-, N-ethyl-and N-cyclohexylmorpholine,N,N,N′,N′-tetramethylethylenediamine, N,N,N′,N′-tetramethylbutanediamineor -hexanediamine, N,N,N′-trimethyl isopropyl propylenediamine,pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether,bis(dimethylaminopropyl)urea, dimethylpiperazine,1-methyl4-dimethylaminoethyl-piperazine, 1,2-dimethylimidazole,1-azabicylo[3.3.0]octane and preferably 1,4-diazabicylol[2.2.2]octane,and alkanolamine compounds, such as triethanolamine,triisopropanolamine, N-methyl- and N-ethyldiethanolamine anddimethylethanolamine.

[0030] A surfactant and/or cell regulator may also be incorporated intothe polyurethane backing layer. Specific examples of surfactants aresalts of sulfonic acids, e.g., alkali metal salts or ammonium salts ofdodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid.Other preferred surfactants include silicone-containing surfactantpolymers. Specific examples of anti-foam agents includesiloxane-oxyalkylene copolymers and other organopolysiloxanes,oxyethylated alkyl-phenols, oxyethylated fatty alcohols, paraffin oils,castor oil esters, ricinoleic acid esters, Turkey red oil and groundnutoil. Specific examples of cell regulators include paraffins, fattyalcohols, and dimethylpolysiloxanes.

[0031] For the purposes of the subject invention, fillers includeconventional organic and inorganic fillers and reinforcing agents. Morespecific examples include inorganic fillers, such as silicate minerals,for example, phyllosilicates such as antigorite, serpentine, hornblends,amphiboles, chrysotile, and talc; metal oxides, such as aluminum oxides,titanium oxides and iron oxides; metal salts, such as chalk, barite andinorganic pigments, such as cadmium sulfide, zinc sulfide and glass,among others; kaolin (china clay), aluminum silicate and co-precipitatesof barium sulfate and aluminum silicate, and natural and syntheticfibrous minerals, such as wollastonite, metal, and glass fibers ofvarious lengths. Examples of suitable organic fillers are carbon black,melamine, colophony, cyclopentadienyl resins, cellulose fibers,polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, andpolyester fibers based on aromatic and/or aliphatic dicarboxylic acidesters, and in particular, carbon fibers.

[0032] Examples of suitable flame retardants are tricresyl phosphate,tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, andtris(2,3-dibromopropyl) phosphate. A suitable flame retardant incompositions of the present invention comprises FYROL® PCF, which is atris(chloro propyl)phosphate commercially available from Albright &Wilson.

[0033] In addition to the above-mentioned halogen-substitutedphosphates, it is also possible to use inorganic or organic flameretardants, such as red phosphorus, aluminum oxide hydrate, antimonytrioxide, arsenic oxide, ammonium polyphosphate (Exolit®) and calciumsulfate, expandable graphite or cyanuric acid derivatives, e.g.,melamine, or combinations of two or more flame retardants, e.g.,ammonium polyphosphates and melamine, and, if desired, corn starch, orammonium polyphosphate, melamine, and expandable graphite and/or, ifdesired, aromatic polyesters, in order to flameproof the polyurethanebacking layer.

[0034] Further details on the other conventional assistants andadditives mentioned above can be obtained from the specialistliterature, for example, from the monograph by J. H. Saunders and K. C.Frisch, High Polymers, Volume XVI, Polyurethanes, Parts 1 and 2,Interscience Publishers 1962 and 1964, respectively, orKunststoff-Handbuch, Polyurethane, Volume VII, Carl-Hanser-Verlag,Munich, Vienna, 1st and 2nd Editions, 1966 and 1983; incorporated hereinby reference.

[0035] The polyisocyanate reacts with the polyol resin, specificallywith the polyol and the other components of the polyol resin, to formthe polyurethane backing layer having urethane linkages. Thepolyisocyanate may also be a pre-polymer. That is, the polyisocyanatemay be a polyisocyanate initiated pre-polymer including thepolyisocyanate in a stoichiometric excess amount and a polyol resincomponent. This polyol resin component of the pre-polymer may be thesame as the polyol resin described above. In any event, thepolyisocyanates utilized in the subject invention preferably have anaverage functionality of greater than 2, most preferably 2.5 or more.This functionality provides for a greater crosslinking density whichimproves the overall dimensional stability of the composite article.

[0036] In a preferred embodiment of the subject invention, thepolyisocyanate is a polymeric diphenylmethane diisocyanate (PMDI) havingan average functionality of about 2.7. A suitable polyisocyanate iscommercially available as ELASTOFLEX® R23000 from BASF Corporation,Wyandotte, Mich. If the polyisocyanate is a polyisocyanate initiatedpre-polymer, then it is preferably a PMDI initiated pre-polymerincluding the PMDI in a stoichiometric excess amount and the polyolresin component of the pre-polymer.

[0037] Other suitable organic polyisocyanates, defined as having 2 ormore isocyanate functionalities, include, but are not limited to,conventional aliphatic, cycloaliphatic, araliphatic and aromaticisocyanates other than PMDI. Specific examples include: alkylenediisocyanates with 4 to 12 carbons in the alkylene radical such as1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate,2-methyl-1,5-pentamethylene diisocyanate, 1,4-tetramethylenediisocyanate, 1,6-hexamethylene diisocyanate; cycloaliphaticdiisocyanates such as 1,3- and 1,4-cyclohexane diisocyanate as well asany combinations of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate as well as thecorresponding isomeric combinations, 4,4′-2,2′-, and2,4′-dicyclohexylmethane diisocyanate as well as the correspondingisomeric combinations and aromatic diisocyanates and polyisocyanatessuch as 2,4- and 2,6-toluene diisocyanate and the corresponding isomericcombinations 4,4′-, 2,4′-, and 2,2′-diphenylmethane diisocyanate and thecorresponding isomeric combinations, combinations of 4,4′-, 2,4′-, and2,2-diphenylmethane diisocyanates and polyphenylenepolymethylenepolyisocyanates (crude MDI), as well as combinations of crude MDI andtoluene diisocyanates. The organic di- and polyisocyanates can be usedindividually or in the form of combinations.

[0038] Additionally, so-called modified multivalent isocyanates, i.e.,products obtained by the partial chemical reaction of organicdiisocyanates and/or polyisocyanates may be used. Examples includediisocyanates and/or polyisocyanates containing ester groups, ureagroups, biuret groups, allophanate groups, carbodiimide groups,isocyanurate groups, and/or urethane groups. More specific examplesinclude organic, preferably aromatic, polyisocyanates containingurethane groups and having an NCO content of 33.6 to 15 weight percent,preferably 31 to 21 weight percent, based on the total weight, e.g.,with low molecular weight diols, triols, dialkylene glycols, trialkyleneglycols, or polyoxyalkylene glycols with a molecular weight of up to6000; modified 4,4′-diphenylmethane diisocyanate or 2,4- and 2,6-toluenediisocyanate, where examples of di- and polyoxyalkylene glycols that maybe used individually or as combinations include diethylene glycol,dipropylene glycol, polyoxyethylene glycol, polyoxypropylene glycol,polyoxyethylene glycol, polyoxypropylene glycol, and polyoxypropylenepolyoxyethylene glycols or -triols. Prepolymers containing NCO groupswith an NCO content of 29 to 3.5 weight percent, preferably 21 to 14weight percent, based on the total weight and produced from thepolyester polyols and/or preferably polyether polyols described above;4,4′-diphenylmethane diisocyanate, combinations of 2,4′- and4,4′-diphenylmethane diisocyanate, 2,4,- and/or 2,6-toluenediisocyanates or polymeric MDI are also suitable. Furthermore, liquidpolyisocyanates containing carbodiimide groups having an NCO content of33.6 to 15 weight percent, preferably 31 to 21 weight percent, based onthe total weight, have also proven suitable, e.g., based on 4,4′- and2,4′- and/or 2,2′-diphenylmethane diisocyanate and/or 2,4′- and/or2,6-toluene diisocyanate. The modified polyisocyanates may optionally bemixed together or mixed with unmodified organic polyisocyanates such as2,4′- and 4,4′-diphenylmethane diisocyanate, polymeric MDI, 2,4′- and/or2,6-toluene diisocyanate.

[0039] To produce the polyurethane backing layer of the subjectinvention, the polyol resin and the polyisocyanate are reacted in suchamounts that a stoichiometric isocyanate index, defined as the number ofequivalents of NCO groups divided by the total number of isocyanatereactive hydrogen atom equivalents multiplied by 100, ranges from about100 to less than about 150, preferably from about 100 to 130, mostpreferably from about 100 to 115.

[0040] The reaction product of the polyol resin and the polyisocyanate,i.e., the polyurethane backing layer, are applied, preferably by sprayapplication, to the UV-cured layer after the UV-curable composition hasbeen applied to the acrylic show surface and is cured thereby formingthe UV-cured layer, which is described below. During application of thepolyurethane backing layer, the volume ratio of the polyol resin to thepolyisocyanate is from 3:1 to 1:3. More preferably, the volume ratio is1.5:1. With this preferred embodiment for the polyol resin and thepolyisocyanate, the volume ratio of 1.5:1 ensures that a stoichiometricexcess of polyisocyanate is present as the polyurethane-based coating isapplied to form the polyurethane backing layer.

[0041] The thickness of the polyurethane backing layer in the completedcomposite article can vary from 1 to 2000 mils. Most preferably, thethickness is from 100 to 400 mils. Furthermore, to balance requiredphysical properties including, but not limited to, rigidity, impactstrength, flexural modulus, and overall durability and support of theacrylic layer, i.e., show surface, the polyurethane baking layer isdesigned to further include chopped fibers as is known in the art toenhance structural integrity. These chopped fibers include, but are notlimited to, chopped fiberglass, chopped carbon fibers, chopped woodfibers, chopped aramid fibers including all aromatic polyamidematerials, chopped polymer fibers such as nylon, and combinationsthereof.

[0042] Preferably, the chopped fiber is chopped fiberglass that ispresent in the polyurethane backing layer in an amount from 1 to 50,more preferably from 15 to 35, parts by weight based on 100 parts byweight of the polyurethane backing layer. Certain embodiments of thesubject invention may include a plurality, i.e., more than onepolyurethane backing layer. In these embodiments, the chopped fibers canbe flattened by rolling prior to application of a subsequentpolyurethane backing layer.

[0043] As initially described above, the UV-curable composition, which,as described below, is formed by the combination of at least one monomerand a curing initiator, is applied between the acrylic layer and thepolyurethane backing layer to enhance bonding between these layers. Assuch, the UV-curable composition may be referred to as a UV-curableprimer composition. The UV-curable composition is preferably formedprior to the application between the acrylic layer and the polyurethanebacking layer.

[0044] However, it is to be understood that the UV-curable compositionmay be formed simultaneous with the application. That is, the at leastone monomer and the curing initiator may be combined to form theUV-curable composition during application. A preferred way to apply theUV-curable composition is to spray apply the UV-curable composition ontothe acrylic layer or the acrylic-based substrate. Of course, it is to beunderstood that other application methods including, but not limited to,wiping, rolling, and brushing, may be utilized to apply the UV-curablecomposition.

[0045] The UV-curable composition includes the at least one monomer. Theat least one monomer includes an ethylenically unsaturated methacrylatemonomer, an ethylenically unsaturated acrylate monomer, or combinationsthereof. Because the at least one monomer is methacrylate oracrylate-based, it is compatible with the acrylic layer. It is believedthat there is an affinity between the methacrylate and acrylate-basedmonomers and the acrylic layer such that, during a dwell time, themonomers of the UV-curable composition can penetrate the interstitialspaces present in the acrylic layer. More specifically, after theUV-curable composition is applied to the acrylic layer, the UV-curablecomposition is allowed to dwell on the acrylic layer for at least 5,preferably for at least 20 minutes, such that the monomer or monomers inthe UV-curable composition can compatibilize with the acrylic layer.That is, the UV-curable composition is permitted to dwell on the acryliclayer for a period of time before the UV-curable composition is exposedto the UV electromagnetic radiation to cure. Exposure of the UV-curablecomposition to UV electromagnetic radiation is described below. It is tobe understood that the period of time that the UV-curable compositiondwells varies depending on the temperature throughout the dwell time.Generally, the higher the temperature, the shorter the dwell time, andvice versa. The temperature throughout the dwell time preferably rangesfrom 67° F. to 120° F.

[0046] The at least one monomer has a hydroxy functional group that isreactive with the polyisocyanate from the polyurethane backing layer.Specifically, the hydroxy functional group of the at least one monomeris reactive with the stoichiometric excess of polyisocyanate that ispresent in the polyurethane backing layer. The UV-curable compositionmay be referred to as a hydroxy-terminated, UV-curable primercomposition. Once the polyurethane backing layer is applied to theUV-cured layer, the hydroxy functional group of the monomer or monomersreacts with isocyanate moieties present in the stoichiometric excess ofpolyisocyanate to establish urethane linkages between the UV-curedlayer, formed from the UV-curable composition, and the polyurethanebacking layer thereby enhancing the bonding between the acrylic layer,which the UV-curable composition has compatibilized with, and thepolyurethane backing layer.

[0047] Overall, the bond between the acrylic layer, i.e., the acrylicshow surface, and the polyurethane backing layer is a cohesive bond.Under testing known in the art, cohesive bonds exhibit cohesive failure,which is a desired physical property. That is, upon attempts to manuallypry apart the discrete layers of the composite article, the acryliclayer and the polyurethane backing layer stick to each other therebydemonstrating that any bond between the acrylic layer and thepolyurethane backing layer, through the UV-cured layer, is stronger thanthe discrete layers themselves. Another particular manner in which thebond between the acrylic layer and the polyurethane backing layer may beevaluated is by measurement with an Instron Tester. With the InstronTester, a tapered blade is utilized to pry apart the bond between theacrylic layer and the polyurethane backing layer. Then, the force, orload, at failure of the bond is measured in lbs. Preferably, the overallbond strength between the acrylic layer and the polyurethane backinglayer, through the UV-cured layer of the subject invention, is resistantto a force of at least 55, more preferably of at least 60, lbs.

[0048] The at least one monomer is preferably selected from at least oneof a hydroxyaliphatic acrylate and a hydroxyaliphatic methacrylate, andhas up to 20 carbon atoms in the alkyl radical. More specifically, theat least one monomer in the UV-curable composition is selected from atleast one of hydroxymethyl methacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxymethylacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutylacrylate, and combinations thereof.

[0049] Overall, the UV-curable composition includes from 1 to 99 partsby weight of the at least one monomer based on 100 parts by weight ofthe UV-curable composition. However, depending on the particularembodiment utilized, the amount of the at least one monomer in theUV-curable composition may vary. In a first embodiment, the UV-curablecomposition includes from 1 to 40, preferably from 5 to 25, parts byweight of the at least one monomer based on 100 parts by weight of theUV-curable composition. In a second embodiment, the UV-curablecomposition includes from 60 to 99, preferably from 75 to 95, parts byweight of the at least one monomer based on 100 parts by weight of theUV-curable composition. The first and second embodiments, as set forthabove, will be described further below.

[0050] Although there may be more than one ethylenically unsaturatedmonomer in the UV-curable composition, a preferred UV-curablecomposition includes only one ethylenically unsaturated monomer,specifically hydroxyethyl methacrylate.

[0051] Other suitable monomers include, but are not limited to,hydroxypropyl methacrylate, butanediol monoacrylate, and glycerindimethacrylate.

[0052] The UV-curable composition also includes a curing initiator. Uponexposure of the UV-curable composition to UV electromagnetic radiation,the curing initiator reacts with the monomer or monomers in theUV-curable composition to cure the UV-curable composition to the acryliclayer thereby forming the UV-cured layer on the acrylic layer. Asdescribed below and as understood by those skilled in the art, the UVelectromagnetic radiation has a wavelength ranging from 10 to 400,preferably from 300 to 400, nanometers (nm). It is to be understood thatin addition to the wavelength range described above, appropriate cure ofthe UV-curable composition to the acrylic layer also depends on otherfactors including, but not limited to, the thickness of the UV-curablecomposition, the temperature, the time and intensity of exposure, andother like factors.

[0053] Preferably, the UV-curable composition includes from 0.05 to 4.0,more preferably from 0.1 to 2.5, parts by weight of the curing initiatorbased on 100 parts by weight of the UV-curable composition.

[0054] In view of the reactivity of the curing initiator when exposed toUV electromagnetic radiation, the curing initiator is further defined asa photo initiator that is reactive with the monomer or monomers in theUV-curable composition upon exposure to UV electromagnetic radiation.More specifically, the photo initiator is reactive with the monomer ormonomers upon exposure to the UV electromagnetic radiation having thewavelength ranging from 10 to 400, preferably from 300 to 400, nm. TheUV-curable composition includes from 0.05 to 4.0, preferably from 0.1 to2.5, parts by weight of the photo initiator based on 100 parts by weightof the UV-curable composition. Generally, the photo initiator includesan acylphosphine oxide. More specifically, a preferred photo initiatorincludes 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide.2,4,6-trimethylbenzoylethoxyphenylphosphine oxide is commerciallyavailable as Lucirin® TPO-L from BASF Corporation. Other suitable photoinitiators include, but are not limited to, benzoin ethers,2,2-dialkyl-2-hydroxyacetophenones, IRGACURE® 500, IRGACURE® 819,IRGACURE® 1700, IRGACURE® 1800, IRGACURE® 1850, and combinationsthereof. The IRGACURE® photo initiators are commercially available fromCiba Specialty Chemicals.

[0055] The UV-curable composition may further include a rheologyadditive. The rheology additive modifies flow of the UV-curablecomposition during cure. Accordingly, the rheology additive is selectedfrom at least one of a reduction agent and a thixotropic agent. Overall,the UV-curable composition includes from 1 to 98 parts by weight of therheology additive based on 100 parts by weight of the UV-curablecomposition. However, as with the at least one monomer, the amount ofthe rheology additive present in the UV-curable composition variesdepending on the particular embodiment.

[0056] In the first embodiment, the rheology additive is further definedas a reduction agent. The reduction agent modifies the flow of theUV-curable composition during cure by reducing a viscosity of theUV-curable composition for appropriate application of the UV-curablecomposition to the acrylic layer. More specifically, if the UV-curablecomposition has a lower viscosity, it is atomized better during sprayapplication such that the UV-curable composition ‘holds-up’ better onvertical surfaces of the composite article and is, therefore, resistantto miscellaneous defects such as sags, drips, and the like. If thereduction agent is present, then the UV-curable composition preferablyincludes from 60 to 98, more preferably from 70 to 90, parts by weightof the reduction agent based on 100 parts by weight of the UV-curablecomposition. Recall that, in this first embodiment, with so muchreduction agent, e.g. from 60 to 98 parts by weight, there may be onlyfrom 1 to 40 parts by weight of the at least one monomer, all based on100 parts by weight of the UV-curable composition.

[0057] The monomer or monomers included in the UV-curable composition,such as hydroxyethyl methacrylate, are preferably in solution with thereduction agent. Preferably, the reduction agent is a solvent, mostpreferably isopropyl alcohol, in an amount from 60 to 98, mostpreferably from 70 to 90, parts by weight of the solvent based on 100parts by weight of the UV-curable composition. Other solvents that maybe used for the reduction agent include, but are not limited to,acetone, methanol, and butylacetate. However, so long as the particularmonomer or monomers selected are soluble in water, then the reductionagent may be water-based. If the reduction agent is not present, or ifthe reduction agent is water-based, then the UV-curable composition maybe formulated to be free of volatile organic compounds (VOCs).

[0058] In the second embodiment, the rheology additive is furtherdefined as a thixotropic agent. Because the thixotropic agent is athixotrope, it inherently modifies the flow of the UV-curablecomposition during cure thereby providing for appropriate application ofthe UV-curable composition to the acrylic layer. With the thixotropicagent, the UV-curable composition can be uniformly applied to thecomposite article and the reduction agent of the first embodiment isgenerally not required. With the thixotropic agent, the UV-curablecomposition ‘holds-up’ better on vertical surfaces of the compositearticle and is, therefore, resistant to miscellaneous defects such assags, drips, and the like. If the thixotropic agent is present, then theUV-curable composition preferably includes from 1 to 15, more preferablyfrom 4 to 9, parts by weight of the thixotropic agent based on 100 partsby weight of the UV-curable composition. Recall that, in this secondembodiment, with so little thixotropic agent, e.g. from 1 to 15 parts byweight, there may be as much as from 60 to 99 parts by weight of the atleast one monomer, all based on 100 parts by weight of the UV-curablecomposition. A preferred thixotropic agent is further defined as fumedsilica, most preferably Aerosil® R 972 which is commercially availablethe Degussa Corporation.

[0059] The UV-curable composition may further include an indicatingagent. The indicating agent indicates if the monomer or monomers havecompatibilized with the acrylic layer. If the indicating agent ispresent in the UV-curable composition, then the UV-curable compositionpreferably includes from 0.05 to 1.0, more preferably from 0.1 to 0.3,parts by weight of the indicating agent based on 100 parts by weight ofthe UV-curable composition. Generally, the indicating agent includes athiophene-based reactive colorant for indicating that the monomer ormonomers have compatibilized with the acrylic layer. The thiophene-basedreactive colorant operates in that an original color of the reactivecolorant is maintained upon exposure to UV electromagnetic radiation ifthe monomer or monomers have compatibilized with the acrylic layer. Onthe other hand, if the monomer or monomers have not compatibilized withthe acrylic layer, then the original color of the reactive colorant isconverted to colorless upon exposure to UV electromagnetic radiation.

[0060] In a preferred embodiment, the original color of the reactivecolorant is blue. Therefore, if the monomer or monomers of theUV-curable composition have compatibilized with the acrylic layer, thenthe original blue color of the reactive colorant is maintained, and ifthe monomer or monomers of the UV-curable composition have notcompatibilized with the acrylic layer, then the original blue color ofthe reactive colorant will convert to colorless. A suitable indicatingagent is commercially available as Reactint® Blue 17AB from MillikenChemical, Division of Milliken & Co., Spartanburg, S.C. This indicatingagent, and others like it, are set forth in U.S. Pat. No. 4,775,748, thedisclosure of which is incorporated herein by reference in its entirety.

[0061] The following examples illustrating the formation of thecomposite article and the UV-curable composition according to thesubject invention, as presented herein, are intended to illustrate andnot limit the invention.

EXAMPLES

[0062] The composite article and the UV-curable composition are preparedby adding and reacting the following parts, by weight, unless otherwiseindicated. TABLE 1A Example 1 Composite Article I Acrylic LayerAcrylic-Based Substrate UV-Cured Layer (formed from the UV- UV-CurableAmount II curable composition) Composition Component (grams) MonomerHydroxyethyl Methacrylate 10.00 [HEMA] Curing Initiator2,4,6-Trimethylbenzoylethoxy-  0.40 phenylphosphine Oxide [TPO-L]Reduction Agent Isopropyl Alcohol [IPA] 89.45 Indicating AgentReactint ® Blue 17AB [17AB]  0.15 Total 100.00  III PolyurethanePolyurethane-Based Coating Backing Layer [See Table 1B Below]

[0063] The polyurethane-based coating is prepared by adding and reactingthe following parts. TABLE 1B POLYURETHANE BACKING LAYER Amount (grams)Polyol Resin POLYOL A 45.58 [a trimethylolpropane initiated polyetherpolyol having a hydroxyl number of about 35, and an averagefunctionality of about 2.5] POLYOL B 19.50 [a vicinaltoluenediamine-initiated polyether polyol having a hydroxyl number ofabout 390, and an average functionality of about 4.0] SUPPLEMENTAL CHAINEXTENDER 15.50 [Diethylene Glycol] FLAME RETARDANT/  5.00 SUPPLEMENTALCROSS-LINKING AGENT [PHT4 Diol] FLAME RETARDANT  5.00 [Fyrol PCF]PIGMENT  3.00 [White Pigment] H2O SCAVENGER  3.00 [Type 3A MolecularSieve] OTHER ADDITIVES  3.42 Polyol Resin Total 100.00  PolyisocyanateISOCYANATE 73.95 [a polymeric diphenylmethane diisocyanate (PMDI)]Polyisocyanate Total 73.95 Total Polyol Resin and Polyisocyanate 173.95 

[0064] The acrylic-based substrate is vacuum formed and then mountedonto a conventional form for support. The UV-curable composition is thensprayed onto the acrylic-based substrate and allowed to dwell or soak onthe acrylic-based substrate for 20 minutes at approximately 80° F. After20 minutes, the UV-curable composition is exposed to UV electromagneticradiation having a wavelength of approximately 380 nanometers to curethe UV-curable composition to the acrylic-based substrate therebyforming the UV-cured layer. The original color of the indicating agent(blue) is maintained, indicating compatibilization of the HEMA monomerin the UV-curable composition with the acrylic-based substrate. Aftercure, the polyurethane backing layer is spray applied onto the curedcomposition and then allowed to cure. After the polyurethane backinglayer cures, the completed composite article is de-molded from theconventional form. The overall bond strength between the acrylic-basedsubstrate and the polyurethane backing layer shows cohesive failure, apositive result, where the acrylic layer and the polyurethane backinglayer stick to each other. Additionally, the overall bond strength ismeasured to be resistant to a force of 70 lbs. with the Instron Testeras described above.

Example 2

[0065] TABLE 2 Example 2 Composite Article I Acrylic Layer Acrylic-BasedSubstrate UV-Cured Layer (formed from the UV- UV-Curable Amount IIcurable composition) Composition Component (grams) Monomer HydroxyethylMethacrylate 20.00 [HEMA] Curing Initiator 2,4,6-Trimethylbenzoylethoxy- 0.10 phenylphosphine Oxide [TPO-L] Reduction Agent Isopropyl Alcohol[IPA] 79.75 Indicating Agent Reactint ® Blue 17AB [17AB]  0.15 Total100.00  III Polyurethane Polyurethane-Based Coating Backing Layer [SeeTable 1B Above]

[0066] The completed composite article of Example 2 is prepared asdescribed above with respect to Example 1 except for a differentUV-curable composition. The overall bond strength between theacrylic-based substrate and the polyurethane backing layer showscohesive failure, a positive result, where the acrylic layer and thepolyurethane backing layer stick to each other. Additionally, theoverall bond strength is measured to be resistant to a force of 70 lbs.with the Instron Tester as described above.

Example 3

[0067] Example 3 Composite Article I Acrylic Layer Acrylic-BasedSubstrate UV-Cured Layer (formed from the UV- UV-Curable Amount IIcurable composition) Composition Component (grams) Monomer HydroxyethylMethacrylate 91.40 [HEMA] Curing Initiator 2,4,6-Trimethylbenzoylethoxy- 1.87 phenylphosphine Oxide [TPO-L] Thixotropic Agent Fumed Silica[Aerosil ®R 972]  6.58 Indicating Agent Reactint ® Blue 17AB [17AB] 0.15 Total 100.00  III Polyurethane Polyurethane-Based Coating BackingLayer [See Table 1B Above]

[0068] The completed composite article of Example 3 is prepared asdescribed above with respect to Example 1 except for a differentUV-curable composition having the thixotropic agent as the rheologyadditive (instead of the reduction agent). The overall bond strengthbetween the acrylic-based substrate and the polyurethane backing layershows cohesive failure, a positive result, where the acrylic layer andthe polyurethane backing layer stick to each other. Additionally, theoverall bond strength is measured to be resistant to a force of 70 lbs.with the Instron Tester as described above.

Example 4

[0069] Example 4 Composite Article I Acrylic Layer Acrylic-BasedSubstrate UV-Cured Layer (formed from the UV- UV-Curable Amount IIcurable composition) Composition Component (grams) Monomer HydroxyethylMethacrylate 92.57 [HEMA] Curing Initiator 2,4,6-Trimethylbenzoylethoxy- 2.00 phenylphosphine Oxide [TPO-L] Thixotropic Agent Fumed Silica[Aerosil ®R 972]  5.28 Indicating Agent Reactint ® Blue 17AB [17AB] 0.15 Total 100.00  III Polyurethane Polyurethane-Based Coating BackingLayer [See Table 1B Above]

[0070] The completed composite article of Example 4 is prepared asdescribed above with respect to Example 1 except for a differentUV-curable composition having the thixotropic agent as the rheologyadditive (instead of the reduction agent). The overall bond strengthbetween the acrylic-based substrate and the polyurethane backing layershows cohesive failure, a positive result, where the acrylic layer andthe polyurethane backing layer stick to each other. Additionally, theoverall bond strength is measured to be resistant to a force of 70 lbs.with the Instron Tester as described above.

[0071] The invention has been described in an illustrative manner, andit is to be understood that the terminology which has been used isintended to be in the nature of words of description rather than oflimitation. Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings, and theinvention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A composite article comprising: an acrylic layer;a polyurethane layer comprising the reaction product of a polyol resinand a stoichiometric excess of polyisocyanate; and a UV-cured layerdisposed between said acrylic layer and said polyurethane layer, formedfrom a UV-curable composition exposed to UV electromagnetic radiation,wherein said UV-curable composition comprises: at least one monomercomprising an ethylenically unsaturated methacrylate monomer, anethylenically unsaturated acrylate monomer, or a combination thereof,wherein said at least one monomer is compatible with said acrylic layerand has hydroxy functional groups reactive with said polyisocyanate, anda curing initiator reactive with said at least one monomer upon exposureto UV electromagnetic radiation.
 2. A composite article as set forth inclaim 1 wherein said UV-curable composition comprises from 1 to 99 partsby weight of said at least one monomer based on 100 parts by weight ofsaid UV-curable composition.
 3. A composite article as set forth inclaim 2 wherein said at least one monomer comprises hydroxyethylmethacrylate or hydroxyethyl acrylate.
 4. A composite article as setforth in claim 2 wherein said at least one monomer is selected from atleast one of hydroxymethyl methacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxymethylacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, andhydroxybutyl acrylate.
 5. A composite article as set forth in claim 2wherein said at least one monomer is selected from at least one ofhydroxyaliphatic acrylate and hydroxyaliphatic methacrylate and has upto 20 carbon atoms in the alkyl radical.
 6. A composite article as setforth in claim 2 wherein said UV-curable composition comprises from 1 to40 parts by weight of said at least one monomer based on 100 parts byweight of said UV-curable composition.
 7. A composite article as setforth in claim 6 wherein said UV-curable composition comprises from 5 to25 parts by weight of said at least one monomer based on 100 parts byweight of said UV-curable composition.
 8. A composite article as setforth in claim 2 wherein said UV-curable composition comprises from 60to 99 parts by weight of said at least one monomer based on 100 parts byweight of said UV-curable composition.
 9. A composite article as setforth in claim 8 wherein said UV-curable composition comprises from 75to 95 parts by weight of said at least one monomer based on 100 parts byweight of said UV-curable composition.
 10. A composite article as setforth in claim 1 wherein said UV-curable composition comprises from 0.05to 4.0 parts by weight of said curing initiator based on 100 parts byweight of said UV-curable composition.
 11. A composite article as setforth in claim 1 wherein said curing initiator is a photo initiatorreactive with said at least one monomer upon exposure to UVelectromagnetic radiation, said photo initiator being present in saidUV-curable composition in an amount from 0.05 to 4.0 parts by weightbased on 100 parts by weight of said UV-curable composition.
 12. Acomposite article as set forth in claim 1 wherein said curing initiatorcomprises 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide or anacylphosphine oxide.
 13. A composite article as set forth in claim 1wherein said curing initiator is reactive with said at least one monomerupon exposure to UV electromagnetic radiation having a wavelengthranging from 10 to 400 nanometers.
 14. A composite article as set forthin claim 1 wherein said curing initiator is reactive with said at leastone monomer upon exposure to UV electromagnetic radiation having awavelength ranging from 300 to 400 nanometers.
 15. A composite articleas set forth in claim 1 wherein said UV-curable composition furthercomprises a rheology additive in an amount of from 1 to 98 parts byweight based on 100 parts by weight of said UV-curable composition. 16.A composite article as set forth in claim 15 wherein said rheologyadditive is selected from at least one of a reduction agent and athixotropic agent.
 17. A composite article as set forth in claim 16wherein said UV-curable composition comprises from 60 to 98 parts byweight of said reduction agent based on 100 parts by weight of saidUV-curable composition.
 18. A composite article as set forth in claim 17wherein said at least one monomer is in solution with said reductionagent.
 19. A composite article as set forth in claim 18 wherein saidreduction agent is water.
 20. A composite article as set forth in claim18 wherein said reduction agent is a solvent.
 21. A composite article asset forth in claim 20 wherein said solvent is isopropyl alcohol.
 22. Acomposite article as set forth in claim 16 wherein said UV-curablecomposition comprises from 1 to 15 parts by weight of said thixotropicagent based on 100 parts by weight of said UV-curable composition.
 23. Acomposite article as set forth in claim 22 wherein said thixotropicagent is fumed silica.
 24. A composite article as set forth in claim 1wherein said UV-curable composition further comprises an indicatingagent in an amount of from 0.05 to 1.0 parts by weight based on 100parts by weight of said V-curable composition.
 25. A composite articleas set forth in claim 24 wherein said indicating agent comprises athiophene-based reactive colorant.
 26. A composite article as set forthin claim 1 wherein said acrylic layer is a show surface of a bathtub.27. A composite article as set forth in claim 1 having a bond strengthbetween said acrylic layer and said polyurethane layer of at least 55lbs.
 28. A composite article comprising: an acrylic layer; apolyurethane layer comprising the reaction product of a polyol resin anda stoichiometric excess of polyisocyanate; and a UV-cured layer disposedbetween said acrylic layer and said polyurethane layer, formed from aUV-curable composition exposed to UV electormagnetic radiation, whereinsaid UV-curable composition comprises: an ethylenically unsaturatedmonomer component selected from at least one of hydroxymethylmethacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate,hydroxybutyl methacrylate, hydroxymethyl acrylate, hydroxyethylacrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate, whereinsaid monomer component is compatible with said acrylic layer and hashydroxy functional groups reactive with said polyisocyanate; a photoinitiator comprising an acylphosphine reactive with said at least onemonomer upon exposure to UV electromagnetic radiation; a rheologyadditive; and an indicating agent comprising a thiophene-based reactivecolorant.
 29. A composite article as set forth in claim 28 wherein saidrheology additive is selected from at least one of a reduction agent anda thixotropic agent.
 30. A method of forming a composite article, saidmethod comprising the steps of: a) providing an acrylic layer; b)applying a UV-curable composition to the acrylic layer wherein theUV-curable composition comprises: at least one monomer comprising anethylenically unsaturated methacrylate monomer, an ethylenicallyunsaturated acrylate monomer, or a combination thereof, wherein the atleast one monomer is compatible with the acrylic layer and has hydroxyfunctional groups, and a curing initiator reactive with the at least onemonomer upon exposure to UV electromagnetic radiation; and c) exposingthe UV-curable composition to UV electromagnetic radiation to cure theUV-curable composition to the acrylic layer and thereby form a UV-curedlayer.
 31. The method of claim 30 further comprising the step of formingthe UV-curable composition by combining the at least one monomer and thecuring initiator prior to step b).
 32. The method of claim 30 furthercomprising the step of allowing the applied UV-curable composition todwell on the acrylic layer prior to step c) until the at least onemonomer compatibilizes with the acrylic layer.
 33. The method of claim32 wherein the step of allowing the applied UV-curable composition todwell on the acrylic layer comprises allowing the applied UV-curablecomposition to dwell on the acrylic layer for at least 5 minutes priorto step c) such that the at least one monomer compatibilizes with theacrylic layer.
 34. The method of claim 30 further comprising the step ofapplying a polyurethane composition to the UV-cured layer after step c),thereby forming a polyurethane layer, said polyurethane compositioncomprising the reaction product of a polyol and a stoichiometric excessof polyisocyanate.
 35. The method of claim 34 wherein the step ofapplying the polyurethane composition comprises applying thepolyurethane composition to the UV-cured layer such that the hydroxyfunctional group of the at least one monomer reacts with isocyanatemoieties in the polyurethane composition.
 36. The method of claim 30wherein the UV-curable composition further comprises a rheologyadditive.
 37. The method of claim 36 wherein the rheology additive isselected from at least one of a reduction agent and a thixotropic agent.39. The method of claim 30 wherein the UV-curable composition furthercomprises an indicating agent.
 40. The method of claim 30 wherein stepc) comprises exposing the UV-curable composition to UV electromagneticradiation having a wavelength ranging from 300 to 400 nanometers to curethe UV-curable composition to the acrylic layer.
 41. The method of claim30 wherein step b) comprises spray applying the UV-curable compositiononto the acrylic layer.
 42. The method of claim 41 further comprisingthe step of applying a polyurethane composition to the UV-cured layerafter step c), thereby forming a polyurethane layer, said polyurethanecomposition comprising the reaction product of a polyol and astoichiometric excess of polyisocyanate.
 43. The method of claim 42wherein the step of applying the polyurethane composition to theUV-cured layer comprises spray applying a polyurethane-based coatingonto the UV-cured layer to form the polyurethane layer after step c).